On screen problem

Hi guys,
This is not a computer question but the TechSpot Board is the only place that I know I can get intelligent information.

I have a Panasonic TV model # CT-32G22V.
Have been using it for years with no problem.
The other day as I was watching the TV a black box showed up on the screen in the lower right of the picture. Like a pop up window.
It says nothing, its just a blank black box. How do I get it off of the screen???

I tried to contact Panasonic but they wanted to charge a ridiculous fee with no guarantee of fixing the problem because the TV is 10 years old.
So here I am bothering you guys hoping someone might have an idea what the fix is.

I grabbed a photo off the web and added the black box exactly how it appears on my TV so you can see what I am talking about.
No matter what input I press, it is always there.
The really strange thing is how I was watching the TV and all of a sudden this black box popped up like it was going to show a message or something but it never did.

Hey thank you so very much for the link and all the info.
I'm going to study the whole page and follow the directions to see if that will fix it.
I'm sitting here thinking how the same day this all started, I was cleaning off a shelf near the TV. On the shelf I found an old remote that had batteries that were leaking.
I now know it was the original remote to the TV. I wonder if when I took out the leaking old batteries...if I may have pressed a button or two. I did not pay any attention because I just took it for granted that the remote was dead because of the bad batteries.

TechSpot Forum is the best!
Thank you for your help and advice 'mailpup'.
The problem was just as you thought, it was the PIP that I did not even know the TV was capable of. [ Picked up the old TV at a yard sale with no info about it].
There must have been just enough juice left in those old leaking batteries to activate one of the buttons while I was removing the batteries.
I got new batteries for the old original remote, followed the instructions on the link you sent me and was able to hit the correct button and erase the black box from off the screen. Problem solved thanks to you guys at TechSpot Forum.